Răspuns :
380=c+r, c-bani cheltuiti, r- bani ramasi
r=c-40
380=c+c-40
420=2c, c=210 lei a avut mama
r=210-40=170 bani ramasi
r=c-40
380=c+c-40
420=2c, c=210 lei a avut mama
r=210-40=170 bani ramasi
380+40=420 lei (ce a cheltuit + ce a ramas) 420:2=210 lei (a avut) 210 -40=170 lei (raman)